Incandescent electric lamp



- FIG-2 FIG-3 Aug. 9, 1938. 'A. VAN DYcK IIJCANDESCEN'I ELECTRIC LAMP tFiled NOV. 12 1937 Patented Aug. 9, 1938 UNITED STATES ICANDESCENT ELECTRIC LAMP Alexandre Van Dyck, Brussels, Belgium Application November 12, 1937, serial No. 174,223

In Belgiumv November 18, 1936l 12 Claims. (Cl. 176-40) This invention relates .to incandescent electric lamps and the like, and concerns in particular the construction yof their illuminantv4 bodies or filaments. y

6 The invention has for its main object to provide a novel method of forming metallic illuminant bodies of refractory materials for incandescent electric lamps and the like, affording a luminous eiliciency at least equal to that of l illuminant bodies constituted by single or double coiling of the usual filaments, while avoiding the disadvantages of these last illuminant bodies;

The illuminant bodies made according to the invention are characterized in that they are oblll tained by means of filaments constituted with line multiple wires, made of refractory materials, coiled, woven,y plaited, superposed or assembled by any convenient means around Ia. mandrel of suitable cross section (or an imaginary core) the mandrel being for example and preferably cylindrical; these filaments 'are presented therefore in the form of a hollow wire composed of multiple elements.

When coiled into a single helix, the hollow filaments constituting the invention form an apparently thick body of the dimensions customary in the art, and having a luminous efficiency at least equallto that of coiled-coil filaments.

'I'he hollow filaments made according to the invention allow of obtaining very easily any desired thickness of wall. 'I'hese vfilaments approximate therefore homogeneous hollow fila- Vments, made in one piece, the manufacture-of which would present insurmountable difficulties by reason of the nature of the material employed.

In the case of helical coiling of the hollow laments made according to the invention, the velements which compose them enjoy a certain reciprocal freedom so that the very objectionable stresses and deformations experienced in the single or double helices formed with a single wire, as explained above, are largely, if not wholly, avoided..

For the same reasons, the waste during they mechanical operation ofcoiling will be greatly reduced, if not suppressed.

lIhere may be adopted, according to the invention, for the manufacture of the hollow filament,

the most varied arrangements of. theLcomponent pitch, so as to obtain crossings` of the elements and tofproduce a sort of plaiting.

The accompanying drawing represents diagrammatically three examples of the formation of hollow filaments according to the invention.

In Fig. 1, ais the mandrel, which supports four lengths of wire-, numbered from 1 to 4, as con- 5 of helices crossing one another. is

Figs. 2 and 3 represent respectively in elevation and in plan a lament composed of multiple lengths of Wire wound in multiple helices opposed so as to form a plaited sheath around the manl drel al.

More generally.: recourse may be had to all the known arrangements adopted for the manufacture of continuous plaited sheaths, which will allow in particular of utilizing existingmachines fed with wires made of suitable refractory metals. 25

Themanufacture of the hollow filaments according to theV invention can beeifectedupon a mandrel of suitable shape, for example cylindrical, which will b'e either removed after completion of the hollow filament or else maintained in 30 this latter. In the rst case, there will be used a mandrel made of materials known in the lamp industry and adaptedto be eliminated', chemically or otherwise, leaving' the material of the illuminant body unattacked, `such as wires of L35 brass, copper, steel, or even refractory metals such as molybdenum. In the second case, re-

'course may be had to mandrels made of infusible and refractory materials, kbad conductors of electricity, but adapted to emit luminous radia-lv 40 tion, like asbestos for example.

The fine wires or component elements of 4the hollow filaments can be of any cross-section whatever, circular, oval, rectangular or other.

For the manufacture ofthe helices, the hollow lament made as explained above `can be coiled to shape, retaining the mandrel which has served for making it, upon a second mandrel of suitable cross-section (or around an imaginarycore) which may have the same properties as thef o0 first man drel. After the ceiling of the helices, these two mandrels (or only one of the two) will be eliminated .in the manner explained1 above or maintained in place.

Fig. 4 of the accompanying drawing shows dla- 55 grammatically and by way of example a hollow filament, made according to the invention, and coiled upon a mandrelb, a being the mandrel which has served for the formation of the hollow body or wire proper.

The vhelical coillng of the hollow filament can be effected upon the machines currently in use for the manufacture of the second helix of the known coiled-coil fllaments, but with infinitely greater facility, having regard to the firmer and more homogeneous nature of the body coiled.

Further, in the manufacture of the hollow illuminant filaments, according to the invention, intended to be coiled like helices, account may be taken of the stresses which arise during this coiling, by means of a suitable arrangement of the component elements. Also provision may be made for a suitable distribution of the constituent elements of the hollow filament in order to obtain such distribution as desired of the radiation in the helices formed; it is clearly possible in this way to increase further the specific efflciency as well as the length of life of the illuminant bodies.

By way of indication, thereI will be given hereafter a comparative example of an illuminant body of the usual kind formed by a single Wire coiled as a helix, which is in turn coiled helically,

, and a hollow filament constituted according to the invention and coiled into a helix.

The two cases refer to an illuminant body made of tungsten for a gas-filled lamp of watts for a voltage of volts, the same weight of tungsten having been utilized for both.

A. Single filament coiled as a double helix.

Total emission surface 65.8 sq. mm.

By the expression total emission surface there is to be understood the enveloping surface of the coiled coil or double helical lament; this imaginary surface constitutes in accordance with the recognized theory of luminous radiation the true emission surface of the filament.

B. Hollow filament made according to the invention and coiled as a helix.

It is easy to deduce from the above data that the sectional area of passage for the current is substantially the mme in the two cases and whereas the same weight of tungsten has been utilized, the total emission surface in the lamp with a hollow filament made according to the invention and Wound as a helix is about 21/2 times greater than in the case of the single filament coiled as a double helix.

It will be observed moreover that since the single filament of the double helix is replaced by a large number of elementary wires, the defects which might be exhibited by one or other or even by several of these Wires will n ot involve the rupture ofthe illuminant body.

If for example, which is relatively. frequent, the single filament of the double helix is badly gauged, a vaporization of the material will be produced in the thinnest zone, and the illuminant body will be destroyed rapidly by the consequentrupture of the filament.

'In the hollow filament made according to the invention and coiled as a helix, a defect of this kind, even if it were to affect several of the elementary wires, could have only a very relative influence, owing to the fact that the aggregate sectional area will be practically unaltered so that the destruction of the illuminant body cannot result therefrom.

The mounting of the illuminant bodies formed with hollow filaments according to the inven' tion can be effected just as in the case of an ordinary filament of the plain coiled or coiledcoil type, that is to say by pinching to the two electrodes and arranged upon suitable supports.

for example consisting of molybdenum wires.

What I claim isz- 1. In the art of incandescent electric lamps, a

filament consisting of an elongated hollow body having its surface formed of refractory metal wires, said body being coiled into a compact shape to constitute the filament.

2. In the art of incandescent electric lamps, a filament consisting of an elongated hollow body having its surface formed of refractory metal wires plaited together, said body being coiled into a compact shape to constitute the filament.

3. In the art of incandescent electric lamps,- a filament consisting of an elongated'hollow body having its surface formed of refractory metal Wires, said body being coiled into helical form to constitute the filament.

4. In the art of incandescent electrlclamps, a

filament composed of refractory metal wires arranged as coaxial helices of long pitch, said wires being plaited together to form a sleeve, and said sleeve being coiled as a helix of short pitch to constitute the filament.

5. In the art of incandescent electric lamps, a filament composed of refractory metal wires arranged as coaxial helices of long pitch, said wires being Woven together to form a sleeve, and said sleeve being coiled as a helix of short pitch to constitute'the filament.

6. In the art of incandescent electric lamps, a fllament composed of refractory metal wires, a group of said wires being arranged as parallel right-handed helices of long pitch, another group of said wires being arranged as parallel lefthanded helices of long pitch, the Wires of said groups being intertwined to form a plaited tubular sleeve, and said sleeve being coiled as a helix of short pitch to constitute the filament.

7. In the art of incandescent electric lamps.' a

lament in the form of a tubular sleeve coiled into a helix with adjacent coils in close relation to one another, the walls of said sleeve consisting of plaited wires of refractory metal.

plaited together to form a sleeve with the wires 8. An incandescent electric `lamp ilament, consisting of a plurality of relatively short and fine wires of refractory metal, said wires being extending in helices of long pitch, and said sleeve being coiled as a helix of short pitch to constitute the filament.

9. An incandescent electric lamp filament. consisting of a plurality of relatively short and fine Wires of refractory metal, said wires being woven together to form a sleeve, and said sleeve being coiled as a helix of short pitch to constitute the filament.

10. An incandescent electric lamp filament, consisting of a plurality of relatively short'and iine wires of refractory metal, said Wires being plaited 4,together around a mandrel to form a sleeve with the wires extending in helices of long electric lampllament,.which comprisesthe steps of drawing fine wire in refractory metal, cutting lengths of said wire. assembling a plurality of lengths ofv said wire aroundamandrel,assembling said lengths to form a tubular sheath, removing said sheath from the mandrel, and ceiling said sheath around a mandrel to constitute a closely coiled hollow body of elongated form having its Walls formed of said refractory metal wires.

12. A 1D0-watt iilament for a 110 volt lamp, consisting of approximately 30 tungsten metal wires plaited into the shape of a sleeve, the die and said sleeve being then closely coiled to form a helix of short pitch, the diameter of said-helix being approximately 1.082 millimeters, and the length of said helix being,l approximately 51 millimeters.

ALEXANDRE VAN DYCK.

fil

,ameter of said wires being approximately 0.012 

